1. Field of the Invention
The present invention relates generally to coal deashing processes and, more particularly but not by way of limitation to improved separation techniques in coal deashing processes.
2. Description of the Prior Art
Various coal deashing processes have been developed in the past wherein coal has been treated with one or more solvents and processed to separate the resulting insoluble coal products from the soluble coal products.
U.S. Pat. Nos. 3,607,716 and 3,607,717 issued to Roach and assigned to the same assignee as the present invention, disclose processes wherein coal is contacted with a solvent and the resulting mixture then is separated into a heavy phase containing the insoluble coal products and a light phase containing the soluble coal products. Other processes for separating the soluble coal products from the insoluble coal products present in coal liquefaction products utilizing one or more solvents are disclosed in U.S. Pat. Nos. 3,607,718 and 3,642,608, both issued to Roach et al., and assigned to the same assignee as the present invention.
While those processes provide a means for substantially separating the soluble coat products from the insoluble coal products, some soluble coal products still are separated with the insoluble materials in the heavy phase. It would be desirable to provide a process to further increase the yield of recoverable soluble coal products by reducing the quantity of soluble coal products separated with the insoluble materials.